This invention generally relates to tube forming mills and, more particularly, to an intermediate transition section for forming a strip of metal having a U-shaped cross-sectional configuration into a tube typically having an annular cross-sectional configuration.
In the manufacture of welded metal tubing formed from a flat strip of material, the use of materials having high yield strength has created problems in the forming operation. More specifically, the high yield strength of the metal strip tends to cause the section being formed to "spring back" thereby causing an undesired cross-sectional configuration presenting alignment of the material being formed prior to its entry into the succeeding forming roll sections, such as passing from the transition section to the fin roll section of the mill.
A production of heavy gauge, large diameter tubing initially requires passing stock to be formed through a number of driven rollers to effect the break down or transformation of the flat strip into a strip of generally U-shaped cross-section. Thence, the U-shaped strip is transformed into a generally annular shaped cross-section by causing the strip to pass through a cluster or transition roll section prior to its entry into a fin roll assembly to assure proper alignment of the abutting edges of the formed strip preparatory to a seam welding operation. In such operations, the mill may be operated at speeds of typically of 80 feet per minute, for example. Accordingly, in the event of a "spring back" of the leading edge of the formed strip prior to entry into the fin roll assembly, the leading edge will strike the rolls causing damage to the leading edge of the strip being formed, the roll surfaces, and the supporting bearings necessitating repair and replacement and costly shut-down time.
These problems are compounded when heavy gauge strip stock is fed into the forming mill in discrete lengths rather than in continuous lengths requiring constant attention to the proper alignment of each length throughout the mill prior to entry into the fin pass rolls to assure to the proper alignment of the abutting edges preparatory to seam welding operations.